RECENT CLIMATE CHANGE IN THE CANADIAN ARCTIC, DOCUMENTED THROUGH CHANGING MICROFOSSIL PROXIES OF THE MACKENZIE SHELF, BEAUFORT SEA

Interest in ice cover and climate in the Arctic has increased in the last few years as a result of a perceived increase of melting in the Arctic ice pack. The instrumental records only cover the last few decades and do not provide the accuracy to determine if this warming is abnormal or part of a large weather pattern that is occurring as a regular event over longer (multidecadal, millennial) time scales. To overcome this we have obtained cores that span the time range into the last glacial with high resolution in the Holocene.

We use a series of microfossil proxies that measure paleo-salinities, temperatures and ice cover that, combined with carbon 14 dating, produce the controls needed to measure these parameters in past climate regimes. These proxies include foraminifera (planktic, benthic), dinoflagellates, and diatoms; the planktic organisms produce the most reliable information for ice cover since they respond to reduced sunlight and benthic foraminifera provide information on salinity as well as sediment input to the high volume Mackenzie River Delta.

In our deepest water core (650m) we see many calcareous foraminifera (both planktic and benthic) in glacial times as there is little runoff. In postglacial times calcareous foraminifera are diminished and replaced by an agglutinated benthic fauna while planktics decrease to nothing in lower salinity caused by the increased river flow of the Mackenzie River. Specific diatom and dinoflagellate species indicate both salinity and ice cover indices over the Holocene with periods showing less ice cover than present. Hence the present ice thinning is not a new phenomenon in the Arctic - the question is the present warming the result of a natural or anthropogenic effect? This work is one of the first to try to answer some of these questions.